KR100490506B1 - Composition for removing residues from the microstructure of an object - Google Patents

Abstract

CO _2, the additives, and the CO ₂ to remove the residue ball for the dissolution of the additives by the step of producing a removing agent comprising a solvent, a pressurized fluid condition, and the object into contact with the removing agent to remove the residues from the object A method and composition are provided for removing residue from a microstructure of an object, the method comprising: An apparatus for carrying out the method is also provided.

Description

COMPOSITION FOR REMOVING RESIDUES FROM THE MICROSTRUCTURE OF AN OBJECT}

The present invention relates to methods and compositions for removing residue from the microstructure of an object. Specifically, the present invention relates to methods and compositions for removing residues such as resists generated during semiconductor manufacturing processes from the surface of semiconductor wafers having microstructures of irregularities.

As a step in the manufacture of semiconductor wafers, photoresists, UV-cured resists, X-ray cured resists, ashed resists, carbon-fluorine-containing polymers, plasma etch residues and organics resulting from other steps of the manufacturing method Or residues such as inorganic contaminants. Dry and wet removal methods are commonly used. In the wet removal method, the semiconductor wafer is immersed in a reagent such as an aqueous solution containing a removal agent to remove residues from its surface. Recently, supercritical CO ₂ is used as such a reagent because of its low viscosity.

However, supercritical CO ₂ by itself is not very sufficient to remove some residue from the surface of the semiconductor wafer. To solve this problem, several additives to supercritical CO ₂ have been proposed. As disclosed in Japanese Patent Laid-Open No. 98-125644, a surfactant or methane having a CF _x group is used as an additive to supercritical CO ₂ . In Japanese Patent Laid-Open No. 96-191063, dimethyl sulfoxide or dimethylformamide is used as such an additive. These additives are not always effective for removing residue.

It is an object of the present invention to provide a composition for efficiently removing residue from the microstructure of an object.

According to the present invention there is provided a process for preparing a remover comprising CO ₂ , an additive for removing residue, and a co-solvent for dissolving the additive in the CO ₂ under pressurized fluid conditions, and contacting an object with the remover. There is provided a method for removing a residue from an object and a composition for use, comprising the step of removing the residue from the object.

And removing the residue from the object, comprising contacting the object with a remover comprising a supercritical CO ₂ , a compound having a hydroxyl group and a fluoride of the general formula NR1R2R3R4F, where R represents hydrogen or an alkyl group. Provide a way to.

In addition, the vessel, CO _2, the ball for the additive and the CO ₂ to remove the residue to dissolve the additives - at least one inlet port for supplying a solvent into said vessel, a pump for pressurizing the CO ₂ into said vessel, and An apparatus is provided for removing residue from an object, including a heater for maintaining the pressurized CO ₂ at a predetermined temperature.

The construction and features of the present invention will become more clearly understood from the following detailed description with reference to the accompanying drawings in which like numerals refer to like elements.

Detailed description of the invention

The present invention applies to the microstructure of an object, for example a semiconductor wafer having a microstructure of irregularities on its surface, and a substrate made of metal, plastic or ceramic, which forms or maintains continuous or discontinuous layers of different materials.

Since pressurized CO ₂ by itself is not sufficient to remove the residue, the pressurized CO ₂ of the present invention with the addition of additives and co-solvents is used as a remover for removing the residue from the object. The additives used for this purpose can remove the residue but by themselves cannot be substantially dissolved in CO ₂ . Co-solvents used for this purpose can dissolve or disperse the additives uniformly in CO ₂ .

Pressurized CO ₂ has a high dispersion rate and can dissolve the dissolved residue therein. When CO ₂ is converted to supercritical conditions, it penetrates more effectively into the fine pattern portion of the object. By this feature, the additive is transferred into the pores or recesses on the surface of the object due to the low viscosity of the CO ₂ .

CO ₂ is pressurized to at least 5 MPa and at least 7.1 MPa at a temperature of 31 ° C. to convert CO ₂ to supercritical fluid conditions.

Preferably, the basic compound is used as an additive because it efficiently hydrolyzes a polymer commonly used as a resist during semiconductor manufacturing. Preferred basic compounds include at least one selected from the group consisting of quaternary ammonium hydroxides, quaternary ammonium fluorides, alkylamines, alkanolamines, hydroxylamines and ammonium fluorides. It is preferred to remove the novolak phenolic resist from the semiconductor wafer using a compound comprising at least one selected from the group consisting of quaternary ammonium hydroxide, quaternary ammonium fluoride, hydroxylamine and ammonium fluoride. The quaternary ammonium hydroxide can be any quaternary ammonium hydroxide such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide (hereinafter TBAH). ) And choline. Quaternary ammonium fluorides may be any quaternary ammonium fluoride such as tetramethylammonium fluoride (hereinafter referred to as TMAF), tetraethylammonium fluoride, tetrapropylammonium fluoride, tetrabutylammonium fluoride and choline fluoride. It may be a ride. The alkylamine may be any alkylamine, for example methylamine, dimethylamine, ethylamine, diethylamine, triethylamine, and propylamine, dipropylamine. Alkanolamines can be any alkanolamines, such as monoethanolamine, diethanolamine, and triethanolamine.

The additive is preferably added at a rate of at least 0.001% by weight, more preferably at least 0.002% by weight of the remover. When the additive is added in a large proportion than 8% by weight, co-solvent should be added more, but the CO ₂ The amount of added co-reduced according to the amount of solvent, which reduces the penetration of the inside surface of the CO ₂ object Let's do it. The upper limit of the additive is 8% by weight, preferably 6% by weight, more preferably 4% by weight.

According to the invention, the co-solvent is added to the CO ₂ with additives. Co-solvents of the invention are compounds that have an affinity for both CO ₂ and additives. These co-solvents dissolve or disperse the additives uniformly in pressurized CO ₂ in fluid conditions. Alcohol, dimethylsulfoxide or mixtures thereof are used as co-solvent. The alcohol is any alcohol, for example ethanol, methanol, n-propanol, iso-propanol, n-butanol, iso-butanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and hexafluoro isopropanol, preferably Preferably ethanol and methanol.

The type and amount of co-solvent is selected according to the type and amount of additives added to CO ₂ . The amount of co-solvent is preferably at least five times that of the additive because the remover becomes easily homogeneous and transparent. Optionally, the remover may comprise 1 to 50 weight percent co-solvent. If more co-solvent is added than 50% by weight, the penetration rate of the remover decreases because of the smaller amount of CO ₂ . It is preferred to use a remover comprising CO ₂ , an alcohol as a co-solvent, a quaternary ammonium fluoride as an additive and / or a quaternary ammonium hydroxide, which are well dissolved in CO ₂ by the alcohol and the CO ₂ -because it is affinity.

According to the present invention, a compound comprising a fluoride and a hydroxyl group of CO ₂ , of the general formula NR 1 R ₂ R 3 R 4 F, wherein R is hydrogen or an alkyl group, while increasing the pressure of CO ₂ or preferably maintaining supercritical conditions Preference is given to contacting with a remover consisting of: Such removers are more efficient in removing ashed residues from semiconductor wafers. The fluoride can be any fluoride of the general formula NR1R2R3R4F, wherein R is hydrogen or an alkyl group, for example ammonium fluoride, tetramethylammonium fluoride, and tetraethylammonium fluoride. It is preferable to use fluoride in which R is an alkyl group because it is CO ₂ -affinity, for example, tetramethylammonium fluoride and tetraethylammonium fluoride. In the present invention, the scavenger may comprise fluoride in 0.001 to 5% by weight, more preferably 0.002 to 0.02% by weight of the scavenger.

Fluoride may be a compound having a hydroxyl group, for example alcohol (e.g., ethanol, methanol, n-propanol, isopropanol, n-butanol and isobutanol, phenol), glycol (e.g., ethylene glycol and methylene glycol And polyethylene glycol) as an additive to supercritical CO ₂ . Alcohols are preferred because they dissolve or disperse fluoride, for example TMAF efficiently and uniformly in supercritical CO ₂ . Ethanol is preferred in alcohols because large amounts of fluoride, for example TMAF, can be dissolved in supercritical CO _{2 in} the presence of ethanol. The concentration of the compound in supercritical CO ₂ depends on the type and concentration of fluoride and the type of residue. Approximately, the compound is preferably included in 1 to 20% by weight of the remover in supercritical CO ₂ .

Supercritical CO _{2 preferably further} comprises dimethylacetamide (hereinafter referred to as “DMAC”). The DMAC contained in CO ₂ is preferably 6 to 70 times the weight of fluoride contained in CO ₂ . It is also desirable that the supercritical CO ₂ be substantially free of water (which is a barrier to manufacturing semiconductor wafers).

1 shows a simplified schematic of the use of a device for removing residue according to the invention. First, a semiconductor wafer having residues on the surface is introduced into a high pressure vessel 9 and placed therein, and then CO ₂ is supplied from the CO ₂ cylinder 1 to the high pressure vessel 9 by the high pressure pump 2. . The high pressure vessel 9 is automatically thermostated to a specific temperature by the thermostat 10 to maintain pressurized CO ₂ in the high pressure vessel 9 at supercritical conditions. The line mixer 11 on the path to the high pressure vessel 9 with the additive and co-solvent while supplying the additive and co-solvent from the tanks 3 and 6 to the high pressure vessel 9 by the high pressure pumps 4 and 7, respectively. Mix by). The flow rates of the additives and co-solvents are regulated by valves 5 and 8, respectively, to be set to predetermined values. CO ₂ , additives and co-solvents can be fed continuously.

2 shows another embodiment of an apparatus for removing residue in accordance with the present invention. In such an apparatus, the additives are mixed with the co-solvent by the line mixer 11 before being fed into the high pressure vessel 9 so as not to be inhomogeneously contacted. The ratio of additive and co-solvent to be supplied to the high pressure vessel 9 is controlled by the ratio controller 12, which controls the amount of additive and / or co-solvent to supercritical CO _{2 in} the high pressure vessel 9. .

The removal method is carried out at a pressure of 5 to 30 MPa, preferably 7.1 to 20 MPa at a temperature of 31 to 210 ° C. The time required to remove the residue depends on the size of the object, the type and amount of the residue, which usually ranges from 1 minute to several tens of minutes.

The present invention is then described with reference to experiments.

Example

Example 1

This experiment is performed by immersing the object in the additives shown in Table 1 for 20 minutes at atmospheric pressure and at a temperature of 40-100 ° C. The object for this experiment is a silicon wafer with a SiO ₂ layer patterned by development and coated with a novolak phenol type resist that has been treated to form microstructures on the surface by dry etching of fluorine gas. The removal rate of a residue is evaluated by the microscope as a ratio of the surface area in which the residue adheres before and after removal. The symbols "X" and "O" mean that the ratios are less than 90% and 90% or more, respectively. The symbol "Φ" means that the ratio is at least 90% when the additive is diluted 10-fold by a co-solvent such as dimethylsulfoxide.

The results are summarized in Table 1.

As shown in Table 1, alkylamines (eg methylamine and ethylamine), alkanolamines (eg monoethanolamine), quaternary ammonium hydroxides (eg TMAH and choline), Hydroxylamine and ammonium fluoride have high removal performance. In particular, quaternary ammonium hydroxides, hydroxylamines, and ammonium fluorides have good residue removal rates.

Example 2

Experiments to investigate the effect of the co-solvent on the solubility of CO ₂ in the additives are carried out via the apparatus shown in FIG. 5. CO ₂ is introduced into the vessel (9) from the CO ₂ cylinder (1) by a pump (2). The pressure and temperature in the vessel are maintained at 20 MPa and 80 ° C. by the thermostat 10. After the additives and co-solvents are mixed in the proportions as shown in Table 2, the mixture is introduced from the mixing vessel 14 into the vessel 9 by the pump 4. The same amount of CO ₂ as the mixture is withdrawn from the vessel 9 to maintain the pressure at 20 MPa when the mixture is introduced. The effect of the co-solvent, ie whether the additive is dissolved in CO ₂ , is observed through the glass window 13 of the container 9. If the additive is not dissolved in CO ₂ , two phases are observed through the window. The symbol "X" in Table 2 means that two phases are observed. The symbol "O" means that the co-solvent evenly dissolves or disperses the additive in CO ₂ (no two phases are observed).

As shown in Table 2, Experiment Nos. 2-1 to 2-9 confirmed the effect of the co-solvent. The conditions in Test Nos. 2-1 to 2-9 observed through the window were clear and uniform and did not show two phases.

Example 3

Experiments for removing the residue using a remover comprising high pressure CO ₂ , additives and co-solvents are carried out via the apparatus of FIG. 1. The object for this experiment is the same as in Example 1. Table 3 shows the types and concentrations of additives and co-solvents in the remover. In Table 3, the symbols "Φ", "O" and "X" represent residue removal rates of 90% or more, 60% or more and 10% or less, respectively.

As shown in Table 3, in Experiment Nos. 3-1 to 3-4, the residue was effectively removed.

Example 4

Experiments for removing residues from the surface of semiconductor wafers were carried out using a remover comprising additives H, I, G, J, L and K, including fluoride of the general formula NR1R2R3R4F, where R is hydrogen or an alkyl group. do. The composition of the additives is listed in Table 4.

In this experiment, three kinds of silicon wafers A, B and C are used. Such silicon wafers have different patterns on their surfaces and also have different removal characteristics of these resists. Silicon wafers are prepared to produce thermal oxides of silicon on their surface and ground into chips (1 cm x 1 cm). The chip is etched in fluoride gas. The resist on the chip is then ashed by plasma to produce an ashed resist. The chip is placed in the high pressure vessel 9. Solutions of additives H, I, G, J, K and L are each prepared such that the fluoride dissolves in the other ingredients listed in Table 4. This additive is introduced into the high pressure vessel of FIG. 1 together with CO ₂ and ethanol. The temperature of CO _{2 in} the high pressure vessel 9 is 40 ° C., the pressure is 15 MPa, and the time for the chip to contact with CO ₂ is 3 minutes. After taking a chip from the high pressure container 9, it observes with an electron microscope.

The results of these experiments are summarized in Table 5.

The ashed resist on wafer-A is cleaned by both H and I 0.05% by weight, including 5% by weight ethanol dissolved in supercritical CO ₂ . The term "excellent" means that there are no residues on the surface of the silicon wafer (chip). The term "good" means that there are few residues on the surface or almost no pattern disappears. In Run 8 using NH4F, since water-soluble residues newly appear on the surface of the silicon wafer (chip), water washing is necessary to remove the residues. In Runs 1 to 7 and 9 to 14, no water rinsing step following the removal step is necessary. In this case, a solvent, preferably containing no CO ₂ and alcohols (eg, methanol and ethanol), but without water, is used to clean the silicon wafer. In addition, for additives J, K and L, no water is substantially required in both the removal and cleaning steps. This method is excellent because it substantially does not use water, which impedes the manufacture of semiconductor wafers.

Wafer-C contains an ashed resist that is more difficult to remove from the surface of a silicon wafer (chip). To remove this resist, more removal time (three times longer than wafer-B) is required. The result is excellent.

Example 5

Silicon wafers are fabricated to produce thermal oxides of silicon on their surfaces and broken into chips. The chip is placed in the high pressure vessel 9 of FIG. Subsequently, a remover comprising CO ₂ , additives and ethanol is introduced into the high pressure vessel 9. After a few minutes of removal treatment, the chip is taken and the thickness of the thermal oxide on the chip is measured with an ellipseometer. The etch rate of the thermal oxide is measured by dividing the reduction in thickness by the treatment time. In supercritical conditions the temperature of CO ₂ is 40 ° C., the pressure is 15 MPa and the treatment time is 20 to 60 minutes.

These experimental results are summarized in Table 6 below.

The data in Table 6 is shown in FIGS. 3 and 4. As shown in FIG. 3, the etching rate of the thermal oxide depends on the concentration of the additive. In addition, as shown in FIG. 4, if the concentration of the additive is constant, the etching rate changes with the ethanol concentration. The etching rate can be adjusted according to the removal object or the removal method. As can be seen from Figures 3 and 4, the etching rate is controlled by adjusting the concentrations of additives and ethanol, and these ratios.

The principles, preferred embodiments and aspects of the present invention have been disclosed above. However, the subject matter of the invention to be protected is not limited to the particular embodiments disclosed. The embodiments disclosed herein are illustrative and not restrictive. Any modifications and variations can be made by other equivalents used without departing from the spirit of the invention. Accordingly, all such modifications, changes and equivalents are intended to be included within the spirit and scope of the invention as defined in the claims.

According to the present invention, a composition is provided for efficiently removing residues from the microstructure of an object.

1 is a schematic diagram of a residue removing apparatus according to the present invention.

2 is a schematic diagram of another embodiment of a residue removing apparatus according to the present invention.

Figure 3 shows the effect of tetramethylammonium fluoride (hereinafter referred to as "TMAF") concentration on the etch rate.

4 shows the effect of ethanol concentration on the etch rate.

5 is a schematic diagram of another embodiment of a residue removing apparatus according to the present invention.

Claims (18)

carbon dioxide; Additives for removing residues, including fluorides having the general formula NR ₁ R ₂ R ₃ R ₄ F, wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group; And Co-solvent for dissolving the additive in the CO ₂ under pressurized fluid conditions Comprising a composition for removing residue from the microstructure of the object. The method of claim 1, A composition wherein the additive further comprises a basic compound. The method of claim 1, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen. The method of claim 1, R ₁ , R ₂ , R ₃ and R ₄ are alkyl groups. carbon dioxide; Compounds having a hydroxyl group; And Fluorides having the general formula NR ₁ R ₂ R ₃ R ₄ F, wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group Comprising a composition for removing residue from the microstructure of the object. The method of claim 5, wherein A composition further comprising a basic compound. The method of claim 6, The basic compound is selected from quaternary ammonium hydroxides, alkylamines, alkanolamines, hydroxylamines and mixtures thereof. The method of claim 5, wherein And a co-solvent selected from dimethylacetamide, propylene glycol, dimethylsulfoxide, deionized water, acetic acid and mixtures thereof. The method of claim 8, A composition wherein the co-solvent comprises deionized water. The method of claim 8, A composition wherein the co-solvent is substantially free of water. The method of claim 5, wherein R ₁ , R ₂ , R ₃ and R ₄ are hydrogen. The method of claim 5, wherein R ₁ , R ₂ , R ₃ and R ₄ are alkyl groups. The method of claim 5, wherein The fluoride is selected from ammonium fluoride, tetramethylammonium fluoride, tetraethylammonium fluoride, tetrabutylammonium fluoride, tetrapropylammonium fluoride, choline fluoride and mixtures thereof. The method of claim 5, wherein The compound is selected from ethanol, methanol, n-propanol, isopropanol, n-butanol, iso-butanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, hexafluoroisopropanol and mixtures thereof. Carbon dioxide in a pressurized or supercritical fluid state; Fluorides having the general formula NR ₁ R ₂ R ₃ R ₄ F (wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group) and mixtures thereof, and optionally basic compounds Additive to be; And Alcohol, dimethylacetamide, propylene glycol, dimethylsulfoxide, deionized water, acetic acid, acetone, ethanol, propanol, dimethylformamide, N-methyl-2-pyrrolidone, diethylene glycol methyl ether and mixtures thereof Co-solvent Comprising a composition for removing residue from the microstructure of the object. The method of claim 15, A composition in which an additive is dissolved in a co-solvent. Fluorides having the general formula NR ₁ R ₂ R ₃ R ₄ F (wherein R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an alkyl group) and mixtures thereof, and optionally basic compounds 0.001 to 8% by weight of an additive; Alcohol, dimethylacetamide, propylene glycol, dimethylsulfoxide, deionized water, acetic acid, acetone, ethanol, propanol, dimethylformamide, N-methyl-2-pyrrolidone, diethylene glycol methyl ether and mixtures thereof Co-solvent 1-50% by weight; And carbon dioxide Comprising a composition for removing residue from the microstructure of the object. The method of claim 17, Wherein the residue is at least one selected from photoresist, UV-cured resist, X-ray cured resist, ashed resist, carbon-fluorine containing polymer, plasma etch residue, organic process contaminants, and inorganic process contaminants.